Evolution of star formation and gas

Scoville, N. Z.

doi:10.1017/cbo9781139547420.010

Cited by 46 publications

(43 citation statements)

References 92 publications

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“…This so-called radiative trapping of the line photons builds up the radiation field at the frequency of the line, leading to enhanced excitation of the upper state via photon absorption. The escape probability formalism can be used to treat this optically thick situation (see, e.g., Scoville 2013). …”

Section: Molecular Line Emissionmentioning

confidence: 99%

Predicting HCN, HCO⁺, multi-transition CO, and dust emission of star-forming galaxies

Vollmer

Gratier

Braine

et al. 2017

A&A

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High-z star-forming galaxies have significantly higher gas fractions and star-formation efficiencies per molecular gas mass than local star-forming galaxies. In this work, we take a closer look at the gas content or fraction and the associated star-formation rate in main sequence and starburst galaxies at z = 0 and z ∼ 1-2 by applying an analytical model of galactic clumpy gas disks to samples of local spiral galaxies, ULIRGs, submillimeter (smm), and high-z star-forming galaxies. The model simultaneously calculates the total gas mass, Hi/H 2 mass, the gas velocity dispersion, IR luminosity, IR spectral energy distribution, CO spectral line energy distribution (SLED), HCN(1-0) and HCO + (1-0) emission of a galaxy given its size, integrated star formation rate, stellar mass radial profile, rotation curve, and Toomre Q parameter. The model reproduces the observed CO luminosities and SLEDs of all sample galaxies within the model uncertainties (∼0.3 dex). Whereas the CO emission is robust against the variation of model parameters, the HCN and HCO + emissions are sensitive to the chemistry of the interstellar medium. The CO and HCN mass-to-light conversion factors, including CO-dark H 2 , are given and compared to the values found in the literature. All model conversion factors have uncertainties of a factor of two. Both the HCN and HCO + emissions trace the dense molecular gas to a factor of approximately two for the local spiral galaxies, ULIRGs and smm-galaxies. Approximately 80% of the molecular line emission of compact starburst galaxies originates in non-self-gravitating gas clouds. The effect of HCN infrared pumping is small but measurable (10-20%). The gas velocity dispersion varies significantly with the Toomre Q parameter. The Q = 1.5 model yields high-velocity dispersions (v disp 10 km s −1 ) consistent with available observations of high-z star-forming galaxies and ULIRGs. However, we note that these high-velocity dispersions are not mandatory for starburst galaxies. The integrated Kennicutt-Schmidt law has a slope of approximately 1 for the local spirals, ULIRGs, and smm-galaxies, whereas the slope is 1.7 for high-z star-forming galaxies. The model shows Kennicutt-Schmidt laws with respect to the molecular gas surface density with slopes of approximately 1.5 for local spiral galaxies, high-z star-forming galaxies. The relation steepens for compact starburst galaxies. The model star-formation rate per unit area is, as observed, proportional to the molecular gas surface density divided by the dynamical timescale. Our relatively simple analytic model together with the recipes for the molecular line emission appears to capture the essential physics of galactic clumpy gas disks.

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Section: Molecular Line Emissionmentioning

confidence: 99%

Predicting HCN, HCO⁺, multi-transition CO, and dust emission of star-forming galaxies

Vollmer

Gratier

Braine

et al. 2017

A&A

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“…Beside that, we also add data from individual ministarburst regions in a galaxy at z = 1.987 (Zanella et al 2015), in SDP81 galaxy at z = 3.042 (Hatsukade et al 2015), and in Arp 220 (Scoville 2013). …”

Section: Radio Continuummentioning

confidence: 99%

The Scaling Relations and Star Formation Laws of Mini-Starburst Complexes

Nguyen-Luong

Nguyen

Motte

et al. 2016

ApJ

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The scaling relations and the star formation laws for molecular cloud complexes in the Milky Way is investigated using data from the 12 CO 1-0 CfA survey and from the literatures. We compare their masses M gas , mass surface densities Σ Mgas , radii R, velocity dispersions σ, star formation rates SF R, and SFR densities Σ SFR with those of structures ranging from cores, clumps, Giant Molecular Clouds (GMCs), to Molecular Cloud Complexes (MCCs), and to Galaxies, spanning 8 orders of magnitudes in size and 13 orders of magnitudes in mass. MCC are mostly large (R > 50 pc), massive (∼ 10 6 M ⊙ ) gravitationally unbound cloud structures. This results in the following universal relations:Mgas , SF R ∼ M gas 0.9 , and SF R ∼ σ 2.7 .Variations in the slopes and the coefficients of these relations are found at individual scales signifying different physics acting at different scales. Additionally, there are breaks at the MCC scale in the σ − R relation and between the starburst and the normal star-forming objects in the SF R − M gas and Σ SFR -Σ Mgas relations. Therefore, we propose to use the Schmidt-Kennicutt diagram to distinguish the starburst from the normal star-forming structures by applying a Σ Mgas threshold of ∼ 100 M ⊙ pc −2 and a Σ SFR threshold of 1 M ⊙ yr −1 kpc −2 . Mini-starburst complexes are gravitationally unbound MCCs that have enhanced Σ SFR (>1 M ⊙ yr −1 kpc −2 ), probably caused by dynamic events such as radiation pressure, colliding flows, or spiral arm gravitational instability. Because of the dynamical evolution, gravitational boundedness does not play a significant role in characterizing the star formation activity of MCCs, especially the mini-starburst complexes, which leads to the conclusion that the formation of massive stars and clusters is dynamic. We emphasize the importance of understanding mini-starburst in investigating the physics of starburst galaxies.

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“…Even the dusty, metalenriched gas of the current Galactic disc converts to stars extremely slowly in the sense that less than one percent of a molecular cloud is turned into stars in a dynamical time. Moreover, since the overwhelming majority of the gas interior to the Sun is in molecular form, molecular clouds cannot be easily dissociated by star formation: their estimated lifetime is 10 8 yr (Scoville 2013).…”

Section: Lifetime Of the Gas Clumpsmentioning

confidence: 99%

Early flattening of dark matter cusps in dwarf spheroidal galaxies

Nipoti¹,

Binney²

2014

Monthly Notices of the Royal Astronomical Society

104

105

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Simulations of the clustering of cold dark matter yield dark-matter halos that have central density cusps, but observations of totally dark-matter dominated dwarf spheroidal galaxies imply that they do not have cuspy central density profiles. We use analytic calculations and numerical modelling to argue that whenever stars form, central density cusps are likely to be erased. Gas that accumulates in the potential well of an initially cuspy dark-matter halo settles into a disc. Eventually the surface density of the gas exceeds the threshold for fragmentation into self-gravitating clouds. The clouds are massive enough to transfer energy to the darkmatter particles via dynamical friction on a short time-scale. The halo's central cusp is heated to form a core with central logarithmic density slope γ ≈ 0 before stellar feedback makes its impact. Since star formation is an inefficient process, the clouds are disrupted by feedback when only a small fraction of their mass has been converted to stars, and the dark matter dominates the final mass distribution.

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Evolution of star formation and gas

Cited by 46 publications

References 92 publications

Predicting HCN, HCO⁺, multi-transition CO, and dust emission of star-forming galaxies

Predicting HCN, HCO⁺, multi-transition CO, and dust emission of star-forming galaxies

The Scaling Relations and Star Formation Laws of Mini-Starburst Complexes

Early flattening of dark matter cusps in dwarf spheroidal galaxies

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Evolution of star formation and gas

Cited by 46 publications

References 92 publications

Predicting HCN, HCO+, multi-transition CO, and dust emission of star-forming galaxies

Predicting HCN, HCO+, multi-transition CO, and dust emission of star-forming galaxies

The Scaling Relations and Star Formation Laws of Mini-Starburst Complexes

Early flattening of dark matter cusps in dwarf spheroidal galaxies

Contact Info

Product

Resources

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Predicting HCN, HCO⁺, multi-transition CO, and dust emission of star-forming galaxies

Predicting HCN, HCO⁺, multi-transition CO, and dust emission of star-forming galaxies